Molecular Dynamics Simulation Of The Adhesion Between Polythiophene And Semiconductors

Polythiophene(PTh)materials have developed significant technical interest due to the chain-oriented high thermal conductivity,controllable electrical conductivity and other excellent mechanical properties.Thus,PTh is regarded as a more promising candidate for the electronic devices packaging in the future.In the electronic packaging field,conductive adhesives are commonly used for the connection between semiconductor components.Adhesion is a multifaceted phenomenon and relies on various factors such as substrate structure,temperature and humidity.In order to understand the adhesion mechanism between conductive polymers and different semiconductor materials,it is necessary to carry on deep research on the adhesion between them,providing a theoretical basis for the design of engineering application of conductive adhesives.Steered molecular dynamics(SMD)is used in this paper to study the interfacial adhesion between polythiophene and three semiconductors(silicon,silicon carbide,and diamond),and the energy changes during the separation process are decomposed in detail,so as to further analyze the adhesion mechanism.The innovation of this work includes two aspects.On one hand,entropy change of the polythiophene chain is introduced to study its effect on adhesion;on the other,the source and difference of electrostatic effect is analyzed from the perspective of electronegativity.It is found that both van der Waals interaction and electrostatic interaction both positively contribute to the adhesion between polythiophene and semiconductors while the entropy change of polythiophene weakens the adhesion to some extent.In addition,entropy change can be divided into vibration entropy changes and conformational entropy changes,where vibration entropy change occupied a more important position.It is also found that different practical conditions all have a great influence on the adhesion.The temperature has similar effect on these three systems.When the temperature rises,the adhesion of these systems shows a monotonous decrease in the test range.Also,the influence of crystal surface orientation is very obvious,leading to a markable difference among adhesions in different systems.Functional groups strikingly affect the adhesion energies of different systems as well.The presence of hydroxyl and carboxyl groups largely enhances the adhesion between polythiophene and semiconductors,a significant increase of van der Waals energy,electrostatic energy and vibration entropy results in a significant increase in the overall entropy change.The number of polythiophene chains can also have a great impact on adhesion in this work,for the reason that a competitive relationship is formed between cohesive interaction and adhesion.The cohesive effect will cause the polythiophene chain to curl into a group,otherwise the polythiophene chains will be prevented from self-assembly,which can improve the actual interface strength.In summary,the study of the adhesion mechanism of polythiophene-semiconductor interface in this paper can provide a theoretical basis for the engineering application of conductive polymer adhesives.